This invention relates to the conversion of chemical energy to electrical energy, and more particularly to a new and improved construction for lithium-iodine cells and method of making the same.
One area of use of the present invention is in providing electrical power safely to inaccessible devices in the human environment, for example to an implanted cardiac pacemaker, although the principles of the invention can be variously applied. Several types of batteries for implantable cardiac pacemakers have been proposed, and recently a lithium-iodine cell has been proposed which advantageously has an open circuit voltage about twice that of the mercury cell, does not generate gas during operation, and has a non-corrosive electrolyte.
A cell has been proposed including a lithium anode and a charge transfer complex of an organic donor component and iodine. In providing such a cell for human implantation, various considerations arise as to size and shape. In particular, such a cell must be relatively small in size to be suitable for implantation while at the same time having a lithium area of sufficient size to give the required level of current capability under load conditions. Furthermore, the cell should have an outer shape which causes little or no discomfort when implanted in the body. Along with these requirements, the cell should be constructed in a manner preventing an internal electrical short circuit arising from migration or flow of the iodine-containing cathode material. In addition, such a cell should be relatively easy and economical to manufacture.